Month: June 2023

Wichert and Aziz (1972) have presented a correlation that allows the use of the Standing-Katz graph (Figure 4-1) in the presence of nonhydrocarbon gases. In this case corrected pseudocritical values are and where the term ε3 is a function of the H2S and CO2 concentrations given by that can also be obtained graphically from Figure 4-3. Figure 4-3. Pseudocritical…

In the absence of detailed composition of a natural gas, Figure 4-2 can be used to relate the gas gravity (to air) with the pseudocritical properties of gas mixtures. Using the results of Example 4-2, the calculated molecular weight is 18.92, leading to γg = 18.92/28.97 = 0.65. From Figure 4-2, ppc = 670 psi and Tpc = 375°R, which compare with 671 psi and…

Several important works have presented correlations for natural gas properties. Following is a summary of these, with brief descriptions of the use of these correlations.

The behavior of natural gas mixtures can be approximated by the real gas law where Z is the compressibility factor, also called the gas deviation factor in the petroleum engineering literature. The universal gas constant, R, is equal to 10.73 psi ft3/lb-mol-°R. Equation (4-2) is a general equation of state for gases. The gas compressibility factor for mixtures of…

Gas gravity, as used in natural gas production and reservoir engineering, is the ratio of the molecular weight of a natural gas mixture to that of air, itself a mixture of gases. Gas gravity is perhaps the most important defining property of a natural gas because almost all properties and, in fact, the actual description…

Natural gas reservoirs produce hydrocarbons that exist primarily in the gaseous phase at reservoir conditions. To predict the gas production rate from these reservoirs, there is a need to review some of the fundamental properties of hydrocarbon gases. This is particularly important (more so than in the case of oil reservoirs) because certain physical properties…